The Hollow Needle by George H. Coxe

No one has seen titan of industry John Caldwell for nine years when he hires Kent Murdock to take his picture. Caldwell is preparing a landmark announcement, and wants Boston’s finest newspaper photographer there to document it. Murdock chafes at the stuffy environment of the Caldwell home—particularly when Caldwell’s heir instructs him to take only one picture. Using an infrared flash, Murdock sneaks a second shot. Less than an hour later, John Caldwell is dead.

Murdock makes a print of his second photo, hoping to find something that explains the strange ways of the Caldwell clan. Before he can examine it, the family’s thugs assault him in the dark room, destroying the picture. The photo is gone, but there’s no stopping Kent Murdock from learning what’s rotten in the Caldwell estate.

“Murdock does not believe the story which is given out for publication, and returns to the Caldwell estate to see if he could learn the truth. . . . What else could you expect in a story about Kent Murdock?” - New York Times